Technical Field. The present invention relates to a device for indicating a multi-position state, such as indicating a locked or open state for a vehicle door lock.
Background Information. The state of the lock, i.e., locked or open, is normally indicated by a mechanical connection between the locking mechanism of the door and the door locking knob. The locking knob is usually arranged on the upper side of the door in close proximity to the locking mechanism so that the connecting mechanism does not have to be complex. When the door lock is locked the locking knob is in a lower position, and when the door lock is open the locking knob is in an upper position. The locking knob is also used for maneuvering the lock from the open to the locked position and vice versa.
One such device for indicating the state of a door lock is disclosed in German Patent No. 44 40 717 C1. Therein a pneumatic central locking system is used whereby a pneumatic servomotor actuates a locking bolt. A pneumatic actuating hose supplies pneumatic pressure to the servomotor. The source of pneumatic pressure is either the vehicle engine or a separate motor, e.g., an electric motor. When the pressure in the actuating hose is increased the door lock is unlocked. At a certain low pressure in the actuating hose the door is locked. Hence, the rest position is a locked door, that is, when there is no pressurized air in the actuating hose. A flexible, pneumatic hose is connected to the actuating hose at a first end and to a pneumatic indicating device at a second end. The indicating device can have at least two positionsxe2x80x94a first position when the pressure in the flexible hose is low (door lock locked), and a second position when the pressure in the flexible hose is high (door lock open). The indicating device may comprise a ball that can be pushed up from a rest position (first position) to a working position (second position) by pressurized air in the flexible hose. Alternatively, the indicating device may comprise a flexible membrane that in the rest position (first position) is placed in contact with the lower part of the indicating device and in the working position (second position) is filled with pressurized air, pushing the membrane out from the indicating device.
A drawback of the device described above occurs when there is a leak in the pneumatic system, disabling the locking function as pressurized air must be supplied constantly in order to keep the door lock in an open position. If a leak occurs when the door lock is required to remain open, it will instead become locked. For this reason, a mechanically operated back-up that is accessible from both inside and outside of the vehicle must be provided. A further possible drawback of the above device is that the system must include some kind of pressurized tank to keep the door lock open when the normal source of pressure is inoperative. If the pressurized tank is inoperative, the pneumatic opening of the lock will not work and the mechanical back-up must be used. In addition, elastic parts made of rubber or soft plastic tend to lose their elasticity during freezing conditions. Consequently, all devices using a flexible element for indicating, such as a membrane having two positions, may experience some functional problems during periods of severe cold.
An electronic system for locking car doors is described in U.S. Pat. No. 4,744,021. A locking pin in the door is guided between two end positions by a drive motor, whereby the position of the locking pin (open/closed) is indicated by lighting a first light emitting diode (LED) when the locking pin is in the open position and a second LED when the locking pin is in the locked position. The first LED is off when the second LED is on, and vice versa. Apparent drawbacks of this solution are that LED""s are less visible during the day than during the night. They also require a constant supply of voltage as long as an indication is required, contributing to vehicle battery drain. This can become a problem when the vehicle is not used over a long period of time.
A general purpose of the present invention is to provide a device for indicating a two-position state that does not require a constant supply of voltage or pressurized air for indicating the position of the lock, and which is clearly visible during the day as well as by night.
According to the present invention these purposes are achieved by an indicating device for indicating a multi-position state. The device may have one or more sensors, one or more bi-stable, magnetic switches, and a control unit. The switches are provided with at least one electromagnet arranged in connection with each individual switch, thereby enabling the switches to switch between two or more (multiple) indicating positions by sending an electric pulse through the electromagnet. The sensors are connected to the control unit, which in turn is connected to the switches. The sensors are arranged to sense which of the two or more positions is the current state of a measured object. The sensors are also arranged to transmit a signal corresponding to the position of the measured object to the control unit. The control unit is arranged to transmit a signal to the electromagnet of the corresponding switch in order to update the indicated state of the switch.
Preferred embodiments of the invention include the device described above wherein the switches also have a magnetic element having a first side and a second side, wherein the first side is provided with a first indicating means and the second side is provided with a second indicating means.
The device above may also have different colors for the first indicating means and the second indicating means. Further, either one or both of the first indicating means and the second indicating means may have a fluorescent color. The first indicating means may include a first, flat circular element and the second indicating mean may include a second, flat circular element. The first indicating means may include a first hemispherical element and the second indicating means may include a second hemispherical element. The first indicating means may include a first semi-cylindrical element and the second indicating mean may include a second semi-cylindrical element.
Another embodiment may include the device of above wherein it is arranged to indicate locked and unlocked states of a locking mechanism in a vehicle.
Another embodiment may be a vehicle including the above disclosed device.